Light-emitting device

ABSTRACT

A light-emitting device includes: a mounting base; a plurality of light-emitting elements mounted on or above the mounting base; a plurality of light-transmissive members respectively disposed on upper surfaces of the plurality of light-emitting elements; a plurality of light guide members respectively covering lateral surfaces of the plurality of light-emitting elements; a plurality of antireflective films respectively disposed on upper surfaces of the plurality of the light-transmissive members; and a covering member covering lateral surfaces of the plurality of antireflective films.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/024,620, filed Jun. 29, 2018, which claims priority to JapanesePatent Application No. 2017-128928, filed on Jun. 30, 2017, thedisclosures of which are hereby incorporated by reference in theirentireties.

BACKGROUND

The present disclosure relates to a method of manufacturing alight-emitting device.

There is proposed a method of manufacturing a light-emitting device thatincludes: a bonding step of bonding a plurality of light-emittingelements directly to a plate-shaped wavelength conversion boardconverting light emitted from the light-emitting elements into lighthaving a different wavelength; an electrode forming step of forming padelectrodes by compression on the surface of each of the plurality oflight-emitting elements bonded to the wavelength conversion board,opposite to the surface bonded to the wavelength conversion board; and afirst separation step of cutting the wavelength conversion board intopieces each having at least one of the light-emitting elements (seeJapanese Unexamined Patent Application Publication No. 2016-115729).

It is an object of an embodiment of the present disclosure to provide amethod of manufacturing a light-emitting device with less mechanicalstress on light-emitting elements at the time of mounting thelight-emitting elements on or above a mounting base by flip-chiptechnology.

SUMMARY

Embodiments of the present disclosure are described below.

According to one embodiment, a method of manufacturing a light-emittingdevice includes: directly bonding a plurality of light-emitting elementsto a light-transmissive member having a plate like shape; forming studbumps on each of a plurality of electrodes on the light-emittingelements after the step of directly bonding; obtaining a plurality oflight-transmissive member on each of which one or more of thelight-emitting elements are bonded, by dividing the light-transmissivemember after the step of forming the stud bumps; and mounting thelight-emitting elements on or above a mounting base by flip-chiptechnique, after the step of obtaining the plurality oflight-transmissive members.

According to certain embodiments of the present disclosure, a mechanicalstress applied on the light-emitting elements may be reduced at the timeof mounting the light-emitting elements on or above the mounting base byflip-chip technology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic perspective view of a light-emitting device 1according to a first embodiment.

FIG. 1B is a schematic plan view of the light-emitting device 1according to the first embodiment.

FIG. 1C is a schematic sectional view taken along line 1C-1C in FIG. 1B.

FIG. 2A is a schematic plan view of a light-emitting element 20 on whichstud bumps 30 are disposed.

FIG. 2B is a schematic partial enlarged view of FIG. 2A.

FIG. 2C is a schematic sectional view taken along line A-A in FIG. 2A.

FIG. 3 is a schematic sectional view of the stud bump 30.

FIG. 4 is a schematic sectional view of a light-emitting device 2according to a second embodiment.

FIG. 5A is a schematic sectional view illustrating a method ofmanufacturing the light-emitting device 1 according to the firstembodiment.

FIG. 5B is a schematic sectional view illustrating the method ofmanufacturing the light-emitting device 1 according to the firstembodiment.

FIG. 5C is a schematic sectional view illustrating the method ofmanufacturing the light-emitting device 1 according to the firstembodiment.

FIG. 5D is a schematic sectional view illustrating the method ofmanufacturing the light-emitting device 1 according to the firstembodiment.

FIG. 5E is a schematic sectional view illustrating the method ofmanufacturing the light-emitting device 1 according to the firstembodiment.

FIG. 5F is a schematic sectional view illustrating the method ofmanufacturing the light-emitting device 1 according to the firstembodiment.

FIG. 5G is a schematic sectional view illustrating the method ofmanufacturing the light-emitting device 1 according to the firstembodiment.

FIG. 5H is a schematic sectional view illustrating the method ofmanufacturing the light-emitting device 1 according to the firstembodiment.

FIG. 5I is a schematic sectional view illustrating the method ofmanufacturing the light-emitting device 1 according to the firstembodiment.

DETAILED DESCRIPTION Light-Emitting Device 1 According to FirstEmbodiment

FIG. 1A is a schematic perspective view of a light-emitting device 1according to a first embodiment. FIG. 1B is a schematic plan view of thelight-emitting device 1 according to the first embodiment. FIG. 1C is aschematic sectional view taken along line 1C-1C in FIG. 1B. Asillustrated in FIG. 1A to FIG. 1C, the light-emitting device 1 accordingto the first embodiment includes: a mounting base 70 having a surface onwhich wirings 80 are formed; a plurality of light-emitting elements 20mounted on or above the mounting base 70 by flip-chip technique; and aplurality of light-transmissive members 10 respectively disposed onupper surfaces of the plurality of light-emitting elements 20. Thelight-emitting elements 20 are bonded to the wirings 80 on the mountingbase 70 with stud bumps 30. Detailed description will be given below.

Light-Transmissive Member 10

The light-transmissive members 10 are in contact with the upper surfacesof the light-emitting elements 20, and allow light emitted from thelight-emitting elements 20 to be transmitted and exit the light-emittingdevice 1. Each of the light-transmissive members 10 has an uppersurface, a lower surface opposed to the upper surface, and lateralsurfaces interposed between the upper surface and the lower surface. Theupper surface serves as a light-emitting surface of the light-emittingdevice 1 through which light from the light-emitting element 20 exitsthe light-emitting device 1. The lower surface is directly bonded to alight-extracting surface of the light-emitting element 20. In a planview, the light-transmissive member 10 has an area larger than thelight-emitting element 20. The light-transmissive member 10 has athickness (i.e., a height from the upper surface to the lower surface)of, for example, 50 μm to 300 μm.

An exemplary material used for the light-transmissive member 10 includea light-transmissive material (e.g., light-transmissive resin, glass,and ceramic) shaped into a plate, the light-transmissive material havinga plate like shape that contains one or more wavelength conversionsubstances, and sintered bodies of wavelength conversion substancesshaped into a plate. Examples of the wavelength conversion substancesinclude oxide-based, sulfide-based, and nitride-based wavelengthconversion substances. Specifically, in the case in which a galliumnitride-based light-emitting element that emits blue light is used forthe light-emitting element 20, one or a combination of the followingwavelength conversion substances may be used: YAG-based and/or LAG-basedwavelength conversion substances that absorb blue light and emit yellowto green light; SiAlON-based (e.g., β-SiAlON) and/or SGS wavelengthconversion substances that emit green light; and SCASN-based and/orCASN-based wavelength conversion substances that emit red light,manganese-activated potassium fluorosilicate-based wavelength conversionsubstances (e.g., KSF-based wavelength conversion substance: K₂SiF₆:Mn),and sulfide-based wavelength conversion substances. Thelight-transmissive member 10 may contain, for example, 2 weight % to 50weight % of the wavelength conversion substances. In addition to suchwavelength conversion substances, the light-transmissive member 10 maycontain various kinds of filler such as light-diffusing substances.

The light-transmissive member 10 is directly bonded to thelight-emitting element 20. In the present disclosure, the phrase“directly bonded” means that interfaces to be bonded (i.e., the uppersurface of the light-emitting element 20 and the lower surface of thelight-transmissive member 10) are bonded by using bonding of atomswithout using a bonding material such as an adhesive. Direct bonding ofthe light-transmissive member 10 and the light-emitting element 20enhances heat dissipation of the light-transmissive member 10 to improvereliability of the light-emitting device 1. Particularly, in the case inwhich the light-transmissive member 10 contains wavelength conversionsubstances, heat generated by the wavelength conversion substances iseffectively dissipated through the light-emitting element 20. Moreover,since the light-transmissive member 10 and the light-emitting element 20are directly bonded without using other material such as an adhesive, itis possible to increase light-extracting efficiency of thelight-emitting device 1.

Light-Emitting Element 20

An example of the light-emitting element 20 include a semiconductorlight-emitting element such as a light-emitting diode.

FIG. 2A is a schematic plan view of the light-emitting element 20 onwhich the stud bumps 30 are disposed. FIG. 2B is a partial enlarged viewof FIG. 2A. FIG. 2C is a schematic sectional view taken along line A-Ain FIG. 2A. As illustrated in FIG. 2A to FIG. 2C, the light-emittingelement 20 includes: a support substrate 21 directly bonded to thelight-transmissive member 10; a semiconductor structure 22 formed on thesupport substrate 21; first electrodes 23; and a second electrode 24.Specifically, the surface of the support substrate 21 opposite to thesurface on which the semiconductor structure 22 is formed serves as theupper surface of the light-emitting element 20, and this upper surfaceis directly bonded to the light-transmissive member 10.

Support Substrate 21

The support substrate 21 may be formed using, for example, a materialthat allows epitaxial growth of the semiconductor structure 22 so as toserve as a growth substrate of the semiconductor structure 22. Examplesof this material include sapphire, spinel, and other insulativesubstrates.

Semiconductor Structure 22

Various semiconductor materials such as Group III-V compoundsemiconductors and Group II-VI compound semiconductors may be used forthe semiconductor structure 22. Specifically, nitride-basedsemiconductor materials represented by In_(x)Al_(Y)Ga_(1-X-Y)N (0≤X,0≤Y, X+Y≤1), such as InN, AlN, GaN, InGaN, AlGaN, and InGaAlN may beused. The semiconductor structure 22 includes a first semiconductorlayer 221 (e.g., an n-type semiconductor layer), an active layer, and asecond semiconductor layer 222 (e.g., a p-type semiconductor layer) insequence from the support substrate 21. Each of these layers may have athickness and a layer structure known in the art.

The semiconductor structure 22 includes a plurality of exposed portionsX where the first semiconductor layer 221 is not covered by the secondsemiconductor layer 222 on an upper side of the second semiconductorlayer 222. Specifically, the exposed portions X are regions where thesecond semiconductor layer 222 and the active layer are entirely removedon the second semiconductor layer 222 of the semiconductor structure 22in the thickness direction in order to expose the surface of the firstsemiconductor layer 221 from the second semiconductor layer 222 and theactive layer. In other words, the semiconductor structure 22 has holesin the surface of the second semiconductor layer 222. Each of the holeshas a bottom where the first semiconductor layer 221 is exposed, and haslateral walls where the second semiconductor layer 222, the activelayer, and the first semiconductor layer 221 are exposed. The firstsemiconductor layer 221 exposed on the exposed portions X iselectrically connected to the first electrodes 23 (described later). Thefirst electrodes 23 connected to the first semiconductor layer 221 isformed on an insulating film 25 (described later) above the secondsemiconductor layer 222.

The shapes, sizes, positions, and number of the exposed portions X maybe set suitably in accordance with the size, shape, electrode pattern,and other factors of the light-emitting element 20 to be produced.

All of the plurality of exposed portions X may have the same shape andsize, and each or some of the exposed portions X may have differentshapes and sizes. Preferably, all of the exposed portions X havesubstantially the same size and shape. The exposed portions X areregions with no active layer, therefore, the plurality of exposedportions X having substantially the same size are regularly arrayed inalignment to reduce localization in light-emitting area and currentsupply. This can mitigate luminance irregularity of the light-emittingelement 20 as a whole.

Examples of the shapes of the individual exposed portions X includecircles, ellipses, and polygons such as triangles, rectangles, andhexagons in a plan view. Among these shapes, circles and shapes close tocircles (e.g., ellipses and polygons with six and more sides and angles)are preferable.

The sizes of the exposed portions X may be adjusted suitably inaccordance with factors such as the plane area of the semiconductorstructure 22 and the required light output or luminance of thelight-emitting element. For example, in the case in which the shapes ofthe exposed portions X in a plan view are circles, the diameters may beapproximately several tens to several hundred μm.

Preferably, the plurality of exposed portions X are formed inside of anouter edge of the semiconductor structure 22. Also preferably, theexposed portions X are regularly arrayed. For example, preferably, theexposed portions X are separate from each other in a plan view. Morepreferably, the exposed portions X are aligned at regular intervals.This can mitigate luminance non-uniformity of the light-emitting element20 to ensure uniform light extraction.

Insulating Film 25

The light-emitting element 20 includes the insulating film 25, whichcovers the semiconductor structure 22 and has openings above theplurality of exposed portions X. Specifically, the insulating film 25covers the upper surface and lateral surfaces of the semiconductorstructure 22 and has the openings above the exposed portions X. With theinsulating film 25 covering the upper surface and lateral surfaces ofthe semiconductor structure 22 and having the openings above the exposedportions X, the first electrodes 23 are formed over a wide range of anupper surface of the insulating film 25.

The insulating film 25 is formed using a material known in the art tohave a thickness securing electric insulation. Specifically, metallicoxides and metallic nitrides may be used for the insulating film 25. Forexample, at least one kind of oxide or nitride selected from the groupconsisting of Si, Ti, Zr, Nb, Ta, and Al may be suitably used.

First Electrode 23 and Second Electrode 24

The light-emitting element 20 includes the first electrodes 23, whichare electrically connected to the first semiconductor layer 221, and thesecond electrode 24, which are electrically connected to the secondsemiconductor layer 222, both disposed on the semiconductor layer 22.The first electrodes 23 and the second electrode 24 are disposed at theupper surface side of the semiconductor structure 22, that is, at thesecond semiconductor layer 222 side opposite to the support substrate21. The first electrodes 23 and the second electrode 24 may respectivelybe not in direct contact with, but electrically connected to, the firstsemiconductor layer 221 and the second semiconductor layer 222 via alight-reflective electrode 26, described below.

The first electrodes 23 and the second electrode 24 may be formed ofsingle-layer film or multilayer film of metals such as Au, Pt, Pd, Rh,Ni, W, Mo, Cr, Ti, Al, and Cu or alloys of these metals. Specifically,these electrodes may be formed of multilayer film such as Ti/Rh/Au,Ti/Pt/Au, W/Pt/Au, Rh/Pt/Au, Ni/Pt/Au, Al-Cu alloy/Ti/Pt/Au, Al—Si—Cualloy/Ti/Pt/Au, and Ti/Rh in sequence from the semiconductor structure22. The thickness may be set at any value used in the art.

In the case in which the semiconductor structure 22 has a rectangular orsubstantially rectangular shape in a plan view, preferably, the firstelectrodes 23 and the second electrode 24 similarly have rectangular orsubstantially rectangular shapes in a plan view. Preferably, within thesingle semiconductor structure 22, a group of the first electrodes 23and a group of the second electrode 24 each arranged in one directionare alternately arranged, as viewed from above. In an exemplaryarrangement, the second electrode 24 is interposed between the firstelectrodes 23 in a plan view.

The first electrodes 23 are electrically connected to the exposedportions X at the second semiconductor layer 222 of the semiconductorstructure 22 described above. In this case, preferably, the firstelectrodes 23 are connected so as to cover a plurality of exposedportions X. More preferably, the first electrodes 23 are integrallyconnected to all of the exposed portions X. Consequently, the firstelectrodes 23 are located not only on the first semiconductor layer 221but also above the second semiconductor layer 222. In this case, withthe insulating film 25, the first electrodes 23 are disposed overlateral walls of the holes that define the exposed portions X (i.e., thelateral surfaces of the active layer and the second semiconductor layer222) and above the second semiconductor layer 222. The secondsemiconductor layer 222 and the first electrodes 23 overlap in a planview, but are insulated from each other by the insulating film 25.

The second electrode 24 is disposed above the second semiconductor layer222 of the semiconductor structure 22, and is electrically connected tothe second semiconductor layer 222. The second electrode 24 may be indirect contact with the second semiconductor layer 222 or may be locatedabove the second semiconductor layer 222 with the light-reflectiveelectrode 26 described below.

Light-Reflective Electrode 26

The light-emitting element 20 includes the light-reflective electrodes26, one of which is interposed between the second electrode 24 and thesecond semiconductor layer 222. Silver, aluminum, and alloys thatcontain one of these metals as a main component may be used for thelight-reflective electrodes 26. In particular, silver and silver alloysare preferable due to their high light reflectance with respect to lightemitted from the active layer. Preferably, the light-reflectiveelectrodes 26 have a thickness such that the light-reflective electrodes26 are capable of effectively reflecting light emitted from the activelayer. For example, preferably, the light-reflective electrodes 26 havea thickness of approximately 20 nm to 1 μm. The larger areas of contactsurface between the light-reflective electrodes 26 and the secondsemiconductor layer 222 are, the more preferable. In view of this,preferably, the light-reflective electrodes 26 are also interposedbetween the first electrodes 23 and the second semiconductor layer 222.Specifically, an overall plane area of the light-reflective electrodes26 is, for example, 50% or more, 60% or more, and 70% or more of a planearea of the semiconductor structure 22.

In the case of the light-reflective electrodes 26 containing silver,protection layers 27 may be provided to cover upper surfaces of thelight-reflective electrodes 26, preferably, the upper surfaces andlateral surfaces of the light-reflective electrodes 26 to prevent ormitigate migration of silver. The protection layers 27 may be made of aconductive member such as a metal or an alloy typically used for anelectrode material, or may be made of an insulating member. Examples ofthe conductive member include a single layer and a multiple layercontaining aluminum, copper, nickel, and other metals. Examples of theinsulating member include similar materials to the above-describedmaterials for the insulating film 25. In particular, SiN is preferable.A film of SiN has high density, therefore, SiN has an advantage ofpreventing or mitigating of intrusion of moisture. The thicknesses ofthe protection layers 27 are, for example, approximately several hundrednm to several μm to effectively prevent or mitigate migration of silver.

In the case of using the insulating member to form the protection layers27, the protection layers 27 have an opening above the light-reflectiveelectrode 26 so as to allow the light-reflective electrode 26 toelectrically connect to the second electrode 24.

In the case in which the light-emitting element 20 includes thelight-reflective electrodes 26 and the protection layers 27 on thesecond semiconductor layer 222, the insulating film 25 covering thesemiconductor structure 22 covers the light-reflective electrodes 26 andthe protection layers 27, and has an opening in a region immediatelyunder the second electrode 24 so as to electrically connect the secondelectrode 24 to the light-reflective electrode 26.

Stud Bump 30

The light-emitting element 20 includes the stud bumps 30 connected tothe first electrodes 23 and the second electrode 24. A plurality of studbumps 30 may be disposed on each of the first electrodes 23 and thesecond electrode 24. The stud bumps 30 are disposed on the firstelectrodes 23 and the second electrode 24 of the light-emitting element20 with high density to increase paths in which heat generated by lightemission of the light-emitting element 20 is dissipated from themounting base 70 through the stud bumps 30. The stud bumps 30 may beformed using, for example, gold, silver, copper, tin, platinum, zinc,nickel, or alloys of these metals.

As illustrated in FIG. 2A and FIG. 2B, the stud bumps 30 are provided soas not to overlap the exposed portions X of the first semiconductorlayer 221 in the light-emitting element 20 in a plan view. Thisarrangement of the stud bumps 30 separated from the exposed portions Xcan prevent or mitigate a crack generated in the light-emitting element20 caused by pressure exerted on the light-emitting element 20 at thetime of formation of the stud bumps 30 and flip-chip mounting of thelight-emitting element 20.

Specifically, as illustrated in FIG. 2A to FIG. 2C, the first electrodes23 of the light-emitting element 20 are formed on the insulating film 25above the second semiconductor layer 222. The insulating film 25 coversthe semiconductor structure 22 and has the openings above the exposedportions X. The first electrodes 23 are electrically connected to thefirst semiconductor layer 221 at the bottoms of the openings. The firstelectrodes 23 are formed on the insulating film 25 that directly orindirectly covers the semiconductor structure 22 so as to cover lateralsurfaces of the exposed portions X (i.e., the lateral walls of the holesthat define the exposed portions X) and the upper surface of the secondsemiconductor layer 222. The semiconductor structure 22 hasstair-step(s) between the exposed portions X and the surface of thesecond semiconductor layer 222, hence a crack may be generated by alarge load applied to the stair-step. In particular, a metallic oxide ora metallic nitride for forming the insulating film 25 is stiffer andmore brittle than metal materials for forming the first electrodes 23and the second electrode 24, a crack is more likely to be generated. Acrack generated in the insulating film 25 may unfortunately cause thefirst electrodes 23 to be electrically connected to the secondsemiconductor layer 222 resulting in a short circuit in thelight-emitting element 20. In an arrangement where the exposed portionsX and the stud bumps 30 overlap each other in a plan view, that is, inthe case in which the stud bumps 30 are disposed right above the exposedportions X in a sectional view, a large load may be applied on theabove-described differences caused by the mechanical stress at the timeof flip-chip mounting. This may disadvantageously make a crack in theinsulating film 25 that covers the semiconductor structure 22. However,arrangement of the stud bumps 30 and the exposed portions X beingdisposed to be separated from each other in a plan view enablesalleviation of a large load exerted on the stair-steps, therebypreventing or discouraging generation of a crack in the insulating film25. “Being separated” or “separated” in the present disclosure refers toan outer edge of each stud bump 30 not overlapping an outer edge of eachexposed portion X in a plan view even after the stud bump 30 spreadslaterally and increase in surface area due to pressure at the time offlip-chip mounting of the light-emitting element 20. A double chain lineL in FIG. 2B indicates a shape of the stud bump 30 after squashed. Asillustrated in FIG. 2B, “being separated” or “separated” in the presentdisclosure refers to the outer edge of the stud bump 30 not overlappingthe outer edge of the exposed portion X in a plan view even after thestud bump 30 is squashed.

FIG. 3 is a schematic sectional view of the stud bump 30. As illustratedin FIG. 3, the stud bump 30 has a center tip that protrudes towardopposite side from the first electrodes 23 and the second electrode 24of the light-emitting element 20, in a sectional view. The stud bump 30having this shape may be formed by, for example, a stud bump bonder anda wire bonding device.

Mounting Base 70

The light-emitting elements 20 are mounted above the mounting base 70with the stud bumps 30 by flip-chip technology. The thickness of themounting base 70 is, for example, approximately 0.2 mm to 5 mm. Anexemplary plane shape of the mounting base 70 includes a circle, anellipse, a polygon such as a rectangle, and another shape resemblingthese shapes. Preferably, the mounting base is in a form of a plate orsheet.

The mounting base 70 may be formed using a material selected fromcomposite materials of, for example, resin (including fiber-reinforcedresin), ceramic, glass, metal, and paper. Among these materials, ceramicis preferable due to its heat resistance and weather resistance.Examples of the ceramic include aluminum oxide, aluminum nitride,zirconium oxide, zirconium nitride, titanium oxide, titanium nitride,and mixtures of these ceramic materials.

The mounting base 70 has the wirings 80 disposed at least on the uppersurface thereof. The light-emitting elements 20 are mounted above thewirings 80 by flip-chip technique. For the wirings 80, any wiring may beemployed insofar as the wirings are capable of supplying current to thelight-emitting elements 20. The wirings 80 may be formed using amaterial and have a thickness and a shape that are usually used in theart. Specifically, examples of the material include metals such ascopper, iron, nickel, chromium, aluminum, gold, silver, platinum,titanium, tungsten, and palladium, and alloys of these metals. Inparticular, preferably, the wirings 80 formed on the upper surface ofthe mounting base 70 has an uppermost surface covered with ahighly-reflective material such as silver or gold to efficiently extractlight from the light-emitting elements 20. The wirings 80 can be formedby methods such as electrolytic plating, electroless plating, vapordeposition, and sputtering. For example, in the case in which gold isused for a material of the stud bumps 30, use of gold for forming theuppermost surface of the wirings 80 can improve bonding strength betweenthe light-emitting elements 20 and the mounting base 70.

The stud bumps 30 on the light-emitting elements 20 are bonded to thewirings 80 by a flip-chip technique, such as ultrasonic bonding. Inaddition to the wirings 80, the mounting base 70 may include a frame andother components for holding a covering member 60 described later.

Antireflective Film 40

In order to increase transmittance of light from the light-emittingelements 20, the light-emitting device 1 may include a antireflectivefilm 40 on the surface of each light-transmissive member 10, opposite tothe surface where the light-emitting element 20 is fixed. Theantireflective films 40 are formed on the light-emitting surface of thelight-transmissive members 10 to improve emission efficiency of lightfrom the light-emitting elements 20 while reducing transmission of lightfrom outside the light-emitting device 1. For the antireflective films40, a single-layer or multi-layer film formed using a light-transmissivematerial such as SiO₂ and ZrO₂ may be used.

Light Guide Member 50

The light-emitting device 1 may include light guide members 50 coveringlateral surfaces of each light-emitting element 20. The light guidemembers 50 cover the lateral surfaces of the light-emitting element 20and a lower surface of each light-transmissive member 10 that is exposedfrom the light-emitting element 20. Such light guide members 50 areprovided to cause light emitted from the lateral surfaces of thelight-emitting element 20 to be appropriately reflected by outersurfaces of the light guide members 50 so as to guide the reflectedlight to the light-transmissive member 10.

Preferably, the light guide members 50 are formed using a resin materialthat is easy to handle and process. An example of the resin materialincludes a resin containing one or more of a silicone resin, a modifiedsilicone resin, an epoxy resin, a modified epoxy resin, an acryl resin,and a fluorocarbon resin or a hybrid resin of these resins. As describedbelow, the light guide members 50 may be formed utilizing viscosity ofthe resin material for the light guide members 50 and wettability withrespect to the light-emitting elements 20.

Covering Member 60

The light-emitting device 1 may include the covering member 60 coveringlateral surfaces of the stud bumps 30. In particular, preferably, thecovering member 60 covers all of; the lateral surfaces of thelight-emitting elements 20; space between the light-emitting elements 20and the mounting base 70; the upper surface of the mounting base 70; andthe lateral surfaces of the stud bumps 30. Thus, light from thelight-emitting elements 20 toward the mounting base 70 is reflected withhigh efficiency.

The covering member 60 may be formed using, for example, a resinmaterial having such properties as light reflectiveness, lighttransmissivity, and light-shielding properties. The resin material forthe covering member 60 may contain at least one of a light-reflectivesubstance, a diffuser, and a colorant. For the resin material andsubstances such as the light-reflective substance, any of resinmaterials and substances usually used in the art may be used. An exampleof the resin material includes a resin containing one or more of asilicone resin, a modified silicone resin, an epoxy resin, a modifiedepoxy resin, and an acryl resin or a hybrid resin of these resins.Examples of the light-reflective substances include titanium oxide,silicon oxide, zirconium oxide, yttrium oxide, yttria-stabilizedzirconia, potassium titanate, alumina, aluminum nitride, boron nitride,and mullite.

The light-emitting device 1 may include components, for example,electronic parts and semiconductor elements such as a protection element90. Preferably, these elements and electronic parts are embedded in thecovering member 60.

With the light-emitting device 1 according to the first embodimentdescribed above, the light-emitting elements 20 on which the stud bumps30 are formed are mounted on the mounting base 70 by flip-chiptechnique, thereby enabling reduction in the mechanical stress on thelight-emitting elements 20 at the time of flip-chip mounting. The studbumps 30 are formed on the light-emitting elements 20, but not on themounting base 70, thereby facilitating accurate positioning of thelight-emitting elements 20 and the stud bumps 30 to each other. Inparticular, in the case in which the light-emitting elements 20 includethe above-described exposed portions X, the stud bumps 30 are easilydisposed to be separated from the exposed portions X. This moreeffectively reduce a possibility of a crack generation in thelight-emitting elements 20 described above.

Light-Emitting Device 2 According to Second Embodiment

FIG. 4 is a schematic sectional view of a light-emitting device 2according to a second embodiment. As illustrated in FIG. 4, thelight-emitting device 2 according to the second embodiment is differentfrom the light-emitting device 1 according to the first embodiment inthat a plurality of light-emitting elements 20 are directly bonded to asingle light-transmissive member 10. In a similar manner to thelight-emitting device 2 according to the second embodiment, using thelight-emitting device 1 according to the first embodiment can reduce amechanical stress on the light-emitting elements 20 at the time offlip-chip mounting. The light-emitting elements 20 and the stud bumps 30are easily accurately positioned to each other. In particular, in thecase in which the light-emitting elements 20 include the above-describedexposed portions X, it is possible to more effectively mitigate a crackgeneration in the light-emitting elements 20 described above.

Method of Manufacturing Light-Emitting Device 1 According to FirstEmbodiment

FIG. 5A to FIG. 5I are schematic sectional views illustrating a methodof manufacturing the light-emitting device 1 according to the firstembodiment. The method of manufacturing the light-emitting device 1according to the first embodiment includes, in this order: directlybonding a plurality of light-emitting elements 20 to alight-transmissive member 10 having a plate like shape; forming studbumps on each of a plurality of electrodes on the light-emittingelements 20; obtaining a plurality of light-transmissive member 10 oneach of which one or more of the light-emitting elements 20 are bonded,by dividing the light-transmissive member; and mounting thelight-emitting elements 20 on or above a mounting base 70 by flip-chiptechnique.

A description of such a method will next be made step by step.

Providing Light-Transmissive Member

First, as illustrated in FIG. 5A, the light-transmissive member 10having a plate like shape is provided.

Directly Bonding

Subsequently, as illustrated in FIG. 5B, the plurality of light-emittingelements 20 are directly bonded to the light-transmissive member 10having a plate like shape. Specifically, the support substrate 21 ofeach of the light-emitting elements 20 is directly bonded to thelight-transmissive member 10. In this manner, before the plurality oflight-emitting elements 20 are directly bonded to the light-transmissivemember 10 before being flip-chip mounted. This can improve positioningaccuracy of the light-emitting elements 20 with respect to the uppersurface of the light-transmissive member 10 (i.e., the light-emittingsurface of the light-emitting device 1) in comparison with the case inwhich an individual light-transmissive member 10 is adhered to each ofthe plurality of light-emitting elements 20 that have been flip-chipmounted.

As a direct bonding method, methods known in the art may be adopted. Forexample, any of surface-activated bonding, hydroxyl group bonding, andatomic diffusion bonding may be adopted. Employing any ofsurface-activated bonding, hydroxyl group bonding, and atomic diffusionbonding can realize integral bonding of the light-emitting elements 20and the light-transmissive member 10 in an environment close to normaltemperature.

Surface-activated bonding is a method of bonding by processing surfacesto-be bonded in a vacuum to make them chemically bonded to each othereasily. Hydroxyl group bonding is a method in which hydroxyl groups areformed on surfaces to-be bonded by, for example, atomic layerdeposition, and the hydroxyl groups on the surfaces are bonded to eachother. Atomic diffusion bonding is a method in which a metal film havinga thickness equivalent to a single atomic layer is formed on each ofsurfaces to-be bonded, and the surfaces are brought into contact to eachother in a vacuum or inert gas atmosphere, to bond metal atoms to eachother.

In order to effectively perform bonding at normal temperature,preferably, the bonding surface of the light-transmissive member 10 andthe bonding surfaces of the light-emitting elements 20 have highflatness. Specifically, an arithmetic average roughness Ra of thebonding surfaces is preferably equal to or less than 1.0 nm, morepreferably, equal to or less than 0.3 nm. As a method of processing thebonding surfaces to have such a roughness, mechanical polishing,chemical polishing, and other known methods may be adopted.

Forming Antireflective Film

After bonding directly and before forming the stud bumps, the method ofmanufacturing the light-emitting device 1 may include forming theantireflective film 40 on the surface of the light-transmissive member10, opposite to the surface on which the light-emitting elements 20 arebonded. In forming the antireflective film, as illustrated in FIG. 5C,the antireflective film 40 is formed on the surface serving as thelight-emitting surface of the light-emitting device 1. The surfaceserving as the light-emitting surface of the light-emitting device 1 isthe surface of the light-transmissive member 10 opposite to the surfaceon which the light-emitting elements 20 are bonded. As described above,before performing directly bonding of the light-transmissive member 10and the light-emitting elements 20, pretreatment for processing thebonding surfaces, such as polishing, is necessary. In polishing, avariance may occur in the thickness of the light-transmissive member 10.This thickness deviation can be fixed by processing, for example,polishing the surface of the light-transmissive member 10 opposite tothe surface on which the light-emitting elements 20 are bonded. That is,the antireflective film 40 is formed after directly bonding thelight-transmissive member 10 and the light-emitting elements 20 so as toperform polishing to address the above-described thickness variance aspretreatment of forming the antireflective film.

Forming Stud Bumps

Subsequently, as illustrated in FIG. 5D, the stud bumps 30 are formed oneach of the light-emitting elements 20. The stud bumps 30 may be formed,for example, by a stud bump bonder or wire bonder on the market.Specifically, a tip of metal wire introduced from a capillary of thestud bump bonder is fused into a ball. Balls thus formed are secured tothe first electrodes 23 and the second electrode 24 of thelight-emitting element 20 by a method such as ultrasonicthermocompression bonding, and the secured balls are separated from themetal wire. In this manner, each stud bump 30 is formed on the firstelectrodes 23 and the second electrode 24 of the light-emitting element20. Each ball is separated preferably as follows: after the ball issecured to the first electrodes 23 or the second electrode 24, thecapillary is moved upwardly while the metal wire is held, and then, thecapillary is moved horizontally to separated the deformed ball byscratching with an edge on the distal end of the capillary in such amanner as to make an upper end of the metal wire relatively flat.

The shape of the formed stud bump 30 may be adjusted suitably by anamount of fused metal wire, a shape of the distal end of the capillary,a magnitude of compression, and other factors. The height of the studbump 30 may be adjusted suitably by, for example, a height of upwardmovement and a timing of horizontal movement of the capillary. The upperend of the stud bump 30 may be subjected to flattening processing, suchas etching, blasting, and polishing. Alternatively, a voltage may beapplied to the formed stud bump 30 to generate spark to fuse andrecrystallize to soften or flatten the upper end of the stud bump 30.

By adopting this method, the stud bump 30 having a center tip protrusionis formed on the light-emitting element 20. The softened upper end ofthe stud bump 30 can facilitate deformation of the upper end to beadhered to the wirings 80 on the mounting base 70 at the time offlip-chip mounting. This ensures bonding with high strength even in roomtemperature.

The interval between the stud bumps 30 may be set suitably in accordancewith a size of the light-emitting element 20, the number of the studbumps 30 to be formed, and other factors. For example, in view of heatdissipation, the larger the area on which the stud bumps 30 are bondedto the light-emitting element 20 is, the more preferable. Consequently,the shorter the interval between the stud bumps 30 formed on theidentical electrode is, the more preferable. In consideration offluidity of a resin material in forming the covering member describedbelow, the stud bumps 30 are preferably separated from each other withan interval so as not to reduce fluidity of the resin material. In viewof these considerations, the interval between the stud bumps 30 is, forexample, approximately 10 μm to 45 μm. As described above, the studbumps 30 are formed on the light-emitting element 20, in thisembodiment. Therefore, the light-emitting element 20 and the stud bumps30 may be positioned relative to each other with high accuracy. This canshorten the interval between the stud bumps 30 while the stud bumps 30are appropriately separated from one another.

In the case in which bumps are formed by plating instead of the studbumps 30, it is necessary to change a design of a mask for forming theplated bumps in accordance with a change of an electrode design of thelight-emitting element 20. This may have a possibility todisadvantageously increase time, labor, and cost. However, use of thestud bumps 30 ensures positioning of the bumps at desired locations onthe light-emitting element 20 without using the mask. In the case inwhich bumps are formed by plating, light-emitting elements with platedbumps and a light-transmissive member are to be directly bonded afterforming the plated bumps. However, in this case, a load caused bydirectly bonding the light-emitting elements to the light-transmissivemember may squash the plated bumps on the light-transmissive member.This may unfortunately result in a possibility to increase heightvariance of the light-emitting elements. Such a possibility is not tooccur according to this embodiment, in which the stud bumps 30 areformed after directly bonding the light-transmissive member 10 and thelight-emitting element 20.

In the case in which stud bumps are formed on a mounting base,positioning of the stud bumps formed on the mounting base to electrodesof each light-emitting element. In other words, in order to position thestud bumps at desired positions on the light-emitting element, variancein positional precision in forming the stud bumps on the mounting base,and variance in positional precision in flip-chip mounting of thelight-emitting element on the stud bumps are both to be taken intoaccount. This increases a restriction on the size of the stud bumps.However, such a restriction is mitigated according to this embodiment,in which the stud bumps 30 are formed on the light-emitting element 20.Only positional precision in forming the stud bumps 30 on thelight-emitting element 20 is needed to be taken into account to set thesize of the stud bumps 30. Moreover, stud bumps 30 having a larger planearea may be arranged at positions on the light-emitting element 20,which do not overlap the exposed portions X as described above. This canincrease the contact areas between the light-emitting elements 20 andthe mounting base 70, thereby improving heat dissipation of thelight-emitting device 1. Furthermore, the stud bumps are highlyprecisely formed at desired positions in accordance with an electrodepattern of the light-emitting element 20, thereby enabling increase, forexample, areas of the light-reflective electrodes 26 and/or the numberof the exposed portions X in the light-emitting element 20. This alsocontributes to improvement of light extraction efficiency andimprovement of current diffusibility of the light-emitting elements 20.

Forming Light Guide Members

After forming the stud bumps 30 and before obtaining a plurality oflight-transmissive members 10, the method of manufacturing thelight-emitting device 1 may include forming the light guide members tocover the lateral surfaces of the plurality of light-emitting elements20 with the light guide members 50. In forming the light guide members,as illustrated in FIG. 5E, the light guide members 50 are formed tocover the lateral surfaces of the plurality of light-emitting elements20. Preferably, a resin material that is easy to handle and process isused for the light guide members 50. In the case of the light guidemembers 50 formed using a resin material, arranging a light-transmissivemember before forming stud bumps may have a possibility to deterioratethe light-transmissive member by heat generated at the time of formingthe stud bumps. However, such a possibility may be mitigated in thisstep at which after forming the stud bumps 30 and before obtaining aplurality of light-transmissive members 10, the lateral surfaces of theplurality of light-emitting elements 20 are covered with the light guidemembers 50.

Dividing

Subsequently, as illustrated in FIG. 5F, the light-transmissive member10 including the light guide members 50 and the light-emitting elements20 with the stud bumps 30 is divided in the an optional position, forexample, in dotted lines in FIG. 5F per each of the light-emittingelements 20. Thus, light-transmissive members 10 each including thesingle light-emitting element 20 are obtained. Division may be performedby a dicing saw or other techniques known in the art.

Flip-Chip Mounting

Subsequently, as illustrated in FIG. 5G and FIG. 5H, each of thelight-emitting elements 20 is mounted on or above the mounting base 70by flip-chip technique. FIG. 5G shows a state before flip-chip mounting.FIG. 5H shows a state after flip-chip mounting. As described above, thestud bumps 30 have center tips that protrude toward opposite side fromthe surface bonded to the light-emitting element 20. The light-emittingelement 20 is flip-chip mounted with these center tip protrusions facingthe mounting base 70. The center tip protrusions are portioned at areaswhere stress generated by bonding is likely to concentrate, wherebymounting with the center tips facing the mounting base 70 can mitigatestress on the light-emitting element 20. Particularly the light-emittingelement 20 is integrally bonded to the light-transmissive member 10 bydirect bonding, an impact at the time of flip-chip mounting can bereleased to the light-transmissive member 10 integrated with thelight-emitting element 20. This reduces stress on the light-emittingelement 20.

As illustrated in FIG. 5H, after flip-chip mounting, the stud bumps 30have squashed shapes. In this regard, as described above, the doublechain lines L in FIG. 2B indicate the squashed shapes of the stud bumps30. As illustrated in FIG. 2B, the stud bumps 30 are separated from theexposed portions X in a plan view even after squashed.

An example of a flip-chip mounting technique is ultrasonic bonding.

Forming Covering member

After flip-chip mounting, the method of manufacturing the light-emittingdevice 1 may include forming the covering member 60 which covers thelateral surfaces of the stud bumps 30. In forming the covering member,as illustrated in FIG. 5I, the covering member 60 is formed to cover thelateral surfaces of the stud bumps 30. The covering member 60 is formedto cover the lateral surfaces of the stud bumps 30 under thelight-emitting elements 20 (i.e., between the light-emitting elements 20and the mounting base 70). The covering member 60 is formed to furthercover lateral surfaces of the light-transmissive members 10 and lateralsurfaces of the light-emitting elements 20 and the light guide members50. At this time, upper surfaces of the light-transmissive members 10(i.e., the surfaces where the antireflective films 40 are formed) areexposed from the covering member 60 to form the light-emitting device 1that has the upper surfaces of the light-transmissive members 10 servingas light-emitting surfaces.

A material used for forming the covering member 60 should easily fill agap between the light-emitting elements 20 and the mounting base 70, andto mitigate generation of voids. From this point of view, the materialof the covering member 60 preferably contains a resin material that hashigh fluidity and cures when irradiated with heat or light. An exampleof the material includes a material with fluidity that has a viscosityof 0.5 Pa·s to 30 Pa·s. A reflection amount and a transmission amount oflight may be changed in accordance with, for example, the content of alight-reflective substance in the material used for forming the coveringmember 60. The covering member 60 preferably contains, for example, 20wt % or more of a light-reflective substance. The covering member 60 maybe molded by methods known in the art, such as injection molding,potting molding, resin printing, transfer molding, and compressionmolding.

In the method of manufacturing the light-emitting device 1 according tothe first embodiment described above, the center tip protrusions of thestud bumps 30 are squashed by the mounting base 70 and the wirings 80,but not by the light-emitting elements 20. This can reduce a mechanicalstress on the light-emitting elements 20 at the time of flip-chipmounting of the light-emitting elements on or above the mounting base.

The method of manufacturing the light-emitting device 2 according to thesecond embodiment includes substantially the same steps as the method ofmanufacturing the light-emitting device 1 according to the firstembodiment except for the above-described dividing step of dividing thelight-transmissive member 10 to obtain a plurality of light-transmissivemembers 10 to each of which two or more light-emitting elements 20 arebonded. Therefore, description on the method of manufacturing thelight-emitting device 2 will be omitted.

Although certain embodiments have been described above, the invention isnot limited to the described embodiments.

What is claimed is:
 1. A light-emitting device comprising: a mountingbase; a plurality of light-emitting elements mounted on or above themounting base; a plurality of light-transmissive members respectivelydisposed on upper surfaces of the plurality of light-emitting elements;a plurality of light guide members respectively covering lateralsurfaces of the plurality of light-emitting elements; a plurality ofantireflective films respectively disposed on upper surfaces of theplurality of the light-transmissive members; and a covering membercovering lateral surfaces of the plurality of antireflective films. 2.The light-emitting device according to claim 1, further comprising:wirings formed on an upper surface of the mounting base, wherein theplurality of light-emitting elements are bonded to the wirings with studbumps.
 3. The light-emitting device according to claim 1, furthercomprising: wirings formed on an upper surface of the mounting base,wherein the plurality of light-emitting elements are bonded to thewirings with stud bumps, wherein intervals between the stud bumps are 10μm to 45 μm.
 4. The light-emitting device according to claim 1, whereinintervals between the plurality of antireflective films are smaller thanintervals between the plurality of light-emitting elements.
 5. Thelight-emitting device according to claim 1, wherein lateral surfaces ofthe plurality of light-transmissive members and lateral surfaces of theplurality of antireflective films are flush with each other.
 6. Thelight-emitting device according to claim 1, wherein the plurality oflight-transmissive members have lateral surfaces of perpendicular to anupper surface of the mounting base, wherein the plurality ofantireflective films have lateral surfaces perpendicular to an uppersurface of the mounting base, wherein the lateral surfaces of theplurality of light-transmissive members and the lateral surfaces of theplurality of antireflective films are flush with each other.
 7. Thelight-emitting device according to claim 1, wherein lateral surfaces ofthe plurality of light-transmissive members, lateral surfaces of theplurality of light guide members and lateral surfaces of the pluralityof antireflective films are flush with each other.
 8. The light-emittingdevice according to claim 1, wherein the plurality of light-transmissivemembers have lateral surfaces of perpendicular to an upper surface ofthe mounting base, wherein the plurality of light guide members havelateral surfaces perpendicular to an upper surface of the mounting base,wherein the plurality of antireflective films have lateral surfacesperpendicular to an upper surface of the mounting base, wherein thelateral surfaces of the plurality of light-transmissive members, thelateral surfaces of the plurality of light guide members and the lateralsurfaces of the plurality of antireflective films are flush with eachother.
 9. The light-emitting device according to claim 1, wherein uppersurfaces of the plurality of antireflective films and an upper surfaceof the covering member are flush with each other.
 10. The light-emittingdevice according to claim 1, wherein the covering member covers spacebetween the light-emitting elements.